This invention relates to inspection methods and apparatus, and more particularly relates to methods and means for inspecting pressurized vessels in situ.
It is well known in the prior art that inspecting pressurized vessels is time-consuming and labor-intensive. It is also well known that such inspection operations are hazardous not only to workers but also to the environment.
It is also well known in the prior art that certain pressure vessels such as railway tankcars must be inspected to comply with federal government regulations intended to prevent contamination and perhaps invasion of the environment by industrial waste and contaminants. Thus, such inspections are unavoidable and must be performed on a regular basis.
Personnel engaged in inspecting pressurized vessels typically are required to wear protective clothing, chemical-resistant gloves and use respiratory devices. Personnel frequently are required to actually enter vessels to ascertain whether there is any contamination and the like therein. Procedures generally followed in the art are thus inherently hazardous and are, of course, unpopular among workers. There have been several attempts in the art to improve inspection methodology by providing apparatus which addresses some of these inherent disadvantages and limitations.
For example, in U.S. Pat. No. 5,068,720, Herlitz et at. teach a video inspection system for hazardous environments which comprises a sealed, pressurized housing with a lens affixed across a view window, and a camera mounted within the housing, for recording visual images. Fiber optics may be use to transmit signals from the camera to a recording device. The Herlitz device appears to fail to provide sufficient panning and tilting maneuverability to view all of the interior surfaces of a pressurized vessel without disturbing the pressurized environment inside the vessel and by being inserted into the vessel through an existing port of entry and the like.
As another example, Canty, in U.S. Pat. Nos. 4,965,601 and 4,977,418, teaches apparatus for viewing inside pressure vessels through an aperture in its side. More particularly, U.S. Pat. No. 4,977,418 discloses a hermetically-sealed, explosion-proof aluminum housing containing a charge coupled device (CCD) camera with a fused lens at its front end. This camera is spring-mounted on slide beatings for focusing, which is achieved by externally adjusting a screw or a servo motor located rearward in the housing. Similarly, U.S. Pat. No. 4,965,601 discloses a viewing unit comprising a CCD or CCTV camera having a fused lens attached immediately in front of a fixed lens. The fixed lens is surrounded by a shoulder with a threaded periphery for attaching it to a corresponding aperture in the vessel. Focusing is achieved by turning the camera relative to a threaded portion of the fixed lens housing. An apparent disadvantage of this embodiment is that them is a tendency to unscrew the fused attachment from the connection with the vessel.
In U.S. Pat. No. 4,302,772, Gillot teaches a device for televisual inspection of a closed cylindrical water-containing pressurizer vessel, wherein the device enters the vessel through an aperture. The Gillot apparatus comprises a television camera suspended from a flexible tube and floodlights, with the flexible tube being oriented over its path into the interior of the vessel by a rigid tubular guide. The tube is caused to rotate about its axis preventing the camera from experiencing axial movement, thereby providing improved televisual data with the vacuum intake manifold.
Similarly, in U.S. Pat. No. 3,780,571, Wiesener discloses an apparatus which is inserted within a nuclear reactor pressure vessel for diagnosing whether routine maintenance is required. The apparatus is designed to operate under typical reactor cooling water without pressurized air. Clark discloses, in U.S. Pat. No. 3,021,386, an apparatus using CCTV to view interior boiler walls and project the images to a remote location without damaging the camera. An elongated lens extending through an aperture provides for view adjustments.
While, as hereinbefore exemplified, practitioners in the art have attempted to improve the means and methods for inspecting pressurized vessels, there has not been an improvement in the art which affords a reliable and convenient procedure for performing such inspection without impacting the pressurized contents of the vessel. Accordingly, these limitations and disadvantages of the prior art are overcome with the present invention, and improved means and techniques are provided which are useful for inspecting pressurized vessels in situ.